Glass Strength
A material is said to be brittle if it breaks before undergoing significant plastic
deformation, which is permanent and non-recoverable. A brittle material is characterized
by the dependence of its mechanical strength on the severity of its surface flaws, which
cause localized stress intensification. The plastic deformation reduces the intensified
stress, resulting in a material property that depends more on its intrinsic properties than
on its surface quality. As a typical brittle material, silica glass has a breaking strength
that is dictated by the severity of its surface flaw, not by the intrinsic strength of Si-O
bonds. As one would expect, the breaking strength of glass varies widely, since the
surface flaws or micro-cracks can be inherent to the glass or a result of external damage.